1. Field of the Invention
This invention relates to electrical switching apparatus(es) such as protective devices and switches used in electric power distribution circuits carrying large currents. More particularly, it relates to a trip mechanism having at least two modes of rotation about at least three pivoting surfaces.
2. Background Information
Electrical switching apparatus for opening and closing electric power circuits typically utilize an energy storage device in the form of one or more large springs to close the contacts of the device into the large currents which can be drawn in such circuits. Such electrical switching apparatus includes power circuit breakers and network protectors which provide protection, and electric switches which are used to energize and deenergize parts of the circuit or to transfer between alternative power sources. These devices also include an open spring or springs which rapidly separate the contacts to interrupt current flowing in the power circuit. As indicated, either or both of the close spring and open spring can be a single spring or multiple springs and should be considered as either even though the singular is hereafter used for convenience. The open spring is charged during closing by the close spring which, therefore, must store sufficient energy to both overcome the mechanical and magnetic forces for closing as well as charging the open springs. Moreover, the close spring is required to have sufficient energy to close and latch on at least 15 times the rated current.
Both tension springs and compression springs have been utilized to store sufficient energy to close the contacts and to charge the open spring. The tension springs are easier to control, but the compression springs can store more energy. In either case, a robust operating mechanism is required to mount and control the charging and discharging of the spring. The operating mechanism typically includes a manual handle, and often an electric motor, for charging the close spring. It also includes a latch mechanism for latching the close spring in the charged state, a release mechanism for releasing the stored energy in the close spring, and an arrangement, a pole shaft for example, for coupling the released energy into the moving conductor assembly supporting the moving contacts of the switch.
The latch mechanism includes a hatchet plate that was fixed to a pivot pin. The pivot pin extended between, and was disposed within aligned openings in, two side plates. The pivot pin was structured to rotate within the aligned openings. While this configuration performs the desired function, if the pivot pin becomes fixed in one position, the hatchet plate may be prevented from rotating. For example, if, over an extended period of time, vibration caused the pivot pin openings to become deformed, the pivot pin may not rotate properly. This disadvantage could be overcome if the hatchet plate had more than one mode of rotation about the longitudinal axis of the pivot pin.
There is, therefore, a need for a pivot pin assembly that allows for more than one mode of rotation of a hatchet plate about the pivot pin.
There is a further need for a pivot pin assembly having at least three pivoting surfaces.
There is a further need for a pivot pin assembly that allows for more than one mode of rotation of a hatchet plate about the pivot pin which can be installed in existing circuit breakers.